Analysis of fault data in urban electric distribution grids: lesson learned from Milan, Italy

Reliability and resilience have been among the most significant concerns for distribution system operators. As a result, in the last decades, many states introduced performance-based regulations to push distribution system operators to effectively evaluate the investments and preventive actions to improve the quality of the service offered to customers. To do that, one of the enabling factors is a preliminary investigation of the distribution network reliability and resilience, passing through a detailed analysis of historical fault data. The article presents the results of a statistical evaluation of real fault data relating to the electricity distribution network of Milan, Italy. Due to the urban nature of the considered distribution network, the analysis mainly focuses on the phenomenon of heatwaves and network resilience. However, some considerations are also given for reliability-related issues. The lessons learned from the investigation represent a valuable input to be used by the local distribution system operators, Unareti, to plan and operate the distribution grid.